Electric-resistance furnace.



No, 757,634. LPATENTED APR. 19',- 1904.

.. B. R PRICE.

ELECTRIC RESISTANCE FURNACE.

APPLICATION FILED APR. 30, 1903. 1

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ELECTRIC RESISTANCE FURNACE. APPLICATION FILED APR. so, 1903. .K0 110mm.zsnnz'rs-snnn'r z.

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UNITED STATES Patented April 19, 1904.

PATENT OFFICE.

EDGAR F. PRICE, OF NIAGARA FALLS, NEW YORK, ASSIGNOR TO UNION CARBIDECOMPANY, OF NIAGARA FALLS, NEW YORK, A CORPORATION OF VIRGINIA.

ELECTRIC-RESISTANCE FURNACE.

SPECIFICATION forming part of Letters Patent No. 757,634, dated April19, 1904.

Application filed April 30, 1903.

To all whom it may concern.-

Be it known that I, EDGAR F. PRICE, a citi' zen of the United States,residing at Niagara Falls, in the county of Niagara and State of NewYork, have invented certain new and useful Improvements inElectric-Resistance Furnaces, of which the following is a specification.

This invention is an electric-resistance fur n'ace for heatingmaterials, especially mixtures of a metallic compound and a reducingagent, and specifically lime and carbon for the production of calciumcarbid. The furnace is designed to effect reactions at hightemperatures, and the construction is such as to facilitate thewithdrawal of any molten products through a tap-hole.

The furnace comprises a resistance-conductor in position to heat thecharge and means for passing through the conductor a plurality ofelectric currents which are superposed in such order that the currentdensity increases through a portion of the conductor in proximity to thecharge, heating it ununiformly. The outlet for the molten product, ifany, is

preferably placed adjacent to the region of maximum current density inthe resistanceconcluctor, so that the product may be heated to a hightemperature, and thereby brought into a highly-fluid condition. Thisfeature is 3 of especial importance in the production of calcium carbid,which attains a fluidity suflicient to permit it to be tapped from afurnace only at very high temperatures.

The invention will be more readily under- 3 5 stood by reference to theaccompanying drawings, in which Figure 1 is a vertical axial section ofa stackfurnace. Fig. 2 is a vertical longitudinal section of ahearth-furnace, and Fig. 3 is a ver- 4 tical section of a furnaceemployinga central resistance-conductor.

The furnace shown in Fig. 1 comprises a vertical stack 1 of refractorynon-conducting material, such as magnesia fire-brick, within which is acontinuous tubular lining 2 of refractory conducting material, such ascarbon. The hearth 3 of the furnace is also of refractory conductingmaterial, such as carbon, and

Serial No. 155,024:- (No model.)

with a bell and hopper charging mechanism .6. A plurality of metal rings7 7 7 2 (shown as three in number) surround the carbon lining 2 and areconnected to one terminal or several terminals of like sign of thesource or sources of electric current. Each of these metal ringspreferably has a central passage 8 for water or-other cooling medium.The other terminal or terminals 9 of the source or sources of electriccurrent are connected to an iron plate 10, which underlies and makesgood electrical contact with the carbon hearth 3. The metal rings 7 7 72 are built into the brick shell 1 of the furnace and are so arrangedand spaced upon the carbon lining 2 that the current flowing throughthis lining acting as a resistance-conductor from the intermediate ring7 to the hearth 3 is superposed upon the current flowing from the upperring 7 through the resistance-conductor to the hearth 3. Similarly, thecurrent flowing from the lower ring 7 to the hearth is superposed uponboth of the currents flowing from the upper ring 7 and the intermediatering 7 to the hearth. It will thus be seen that the density of the totalcurrent flowing through the resistance-conductor increases by steps fromthe upper to the lower end of the conductor, so that it is heatedununiformly. When the furnace is filled with a charge, such as a mixtureof lime and carbon in proper proportion to form calcium carbid, thetemperature of the charge will be gradually raised as it descends withinthe furnace by the heat radiated from the resistance-conductor and bythe hot gases rising from the zone of reduction until the materialsreach a point where they react to form calcium carbid. This carbid maybe allowed to accumulate as a pool in the hearth and drawn off from timeto time through the tap-hole or may be allowed to run out continuouslyas produced. Fresh material is fed in at the top as the charge isreduced and descends within the furnace. The waste gases escape from thetop of the fur- 95 nace through an outlet 11.

The furnace shown in Fig. 2 comprises end walls 12 13, floor 14, androof 15 of refractory non-conducting materials, such as fire-brick. Afeed-hopper 22 and waste-gas pipe 16 pass through the roof. On the floorof the furnace lies a resistanceconductor 17, which may be of loosematerial, such as broken coke. The upper surface of this conductorslopes downwardly from a point beneath the hopper to the discharge endof the furnace. An electrode 18, such as a carbon rod, extends into theresistance-conductor at some point remote from the discharge end of thefurnace and is connected to one terminal of a source of current. Anotherelectrode 19-for example, a carbon slab-is placed in contact with theresistanee-conductor at the discharge end of the furnace and connectedto the other terminal of the dynamo. A third electrode 20, connected toelectrode 18, leads into an intermediate part of theresistance-conductor. The material to be heated 21 is fed into thefurnace through hopper 22 and distributed in a layer upon theresistance-conductor. tric currents are thereupon passed from electrodes18 20 to electrode 19. It will be seen that the electric current flowingthrough the resistance-conductor between the electrodes 20 and 19 issuperposed upon the current flowing between the electrodes 18 and 19,thus heating the conductor ununiformly, the density of the current inthe conductor increasing toward the discharge end of the furnace. Thatportion of the charge 2l-for example, lime and coke-near the electrode19 will soon be brought to a temperature sufficient to cause thematerials to react to form carbid and the carbid to be brought intoamolten condition, whereupon it will flow out from the furnace throughtap-hole 23. The charge 21 is then moved downward upon the conductor andfresh material introduced. If desired, the taphole may be temporarilyclosed by a plug of refractory material and the carbid drawn offintermittently.

The furnace shown in Fig. 3 is a vertical annular stack having a body orshell 25 of refractory material, such as magnesia fire-brick, surroundedby a water-jacket 26, and a hearth 27 of refractory conducting material,such as carbon, supported in an iron casing 28. The hearth has atap-hole 29, which may be closed by a plug 30. The top of the furnace isclosed by a metal dome 31, having charginghoppers 32. A vertical column33 of refractory conducting material, here shown as a tube of carbon, isarranged centrally within the furnace and serves as aresistance-conductor. "he lower end of this conductor is seated in arecess 34 in the carbon hearth, and the upper end of the conductorpasses through an insulating-bushing 35, seated in a central opening-inthe metal dome 31. One terminal, 36, of a source of electric current isconnected to the upper end of the resistance-conductor Elec- 33, and asecond terminal 37 of similar polarity extends down within the tubularconductor, being insulated from its upper portion by rings 38, and isput in electrical contact with the conductor at a point 39 intermediateits upper and lower ends. The other terminal or terminals, 10, of thesource or sources of electric current are connected to the metalliccasing of the carbon hearth. It

will be seen that the electric current flowing from the terminal 37through the lower portion of the resistance-conductor to the hearth issuperposed upon the current flowing from the terminal 36 through theconductor to the hearth, thereby heatingitununiformly. The charge fed inthrough hoppers 32 and lying around the resistance-conductor is thusgradually raised in temperature as it descends within the furnace, andthe temperature in the region of the hearth may be carried to a pointsuflicient to effect reduction and enable any molten product to bewithdrawn through the tap-hole which is adjacent to the region ofmaximum current density.

While in the operation of the furnaces shown and described the moltenproduct flows out through a tap-hole and is therefore specified in theclaims as withdrawn by gravity, it will be understood that in some casesthe movement of the molten material may be assisted by mechanical means.For example, the taphole must be kept clear from obstructions and theflow of the carbid under the action of gravity may be suitablyfacilitated or assisted.

I claim 1. An electric-resistance furnace, comprising a stableresistance-conductor in position to heat the charge, and means forpassing differentquantities of electric current through differentportions of said conductor, thereby producing a varying current densitythrough the conductor and heating it ununiformly, as set forth.

2. An electric-resistance furnace, comprising a stableresistance-conductor in position to heat the charge, means for passingdifferent quantities of electric current through diflerent portions ofsaid conductor, thereby prod ucing a varying current density through thecouductor and heating it ununiformly, and means adjacent to the regionof maximum current density for Withdrawing a product by gravity, as setforth.

3. An electric-resistance furnace, comprising a stableresistance-conductor in position to heat the charge, and means forpassing through said conductor a plurality of electric currentssuperposed in such order that the current density increases through theconductor,there by heating it ununiformly, as set forth.

1. An electric-resistance furnace, comprising a stableresistance-conductor in position to heat the charge, means for passingthrough said conductor a plurality of electric currents superposed insuch order that the current density increases through the conductor,thereby heating it ununiformly, and means adjacent to the region ofmaximum current density for withdrawing a product by gravity, as setforth.

5. An electric-resistance furnace, comprising a stableresistance-conductor in position to heat the charge, and means forpassing through said conductor a plurality of electric currentssuperposed in such order that the current density increases along thepath of the current through the conductor, thereby heating itununiformly, as set forth.

6. An electric-resistance furnace, comprising a stableresistance-conductor in position to heat the charge, means for passingthrough said conductor a plurality of electric currents superposed insuch order that the current density increases along the path of thecurrent through the conductor, thereby heating it unelectric currentssuperposed in such order that i the current density increases throughthe conductor to a point where the heat generated by the resistance ofthe conductor Will cause the materials to react to form carbid, as setforth.

In testimony whereof I affix my signature in presence of tWo Witnesses.

EDGAR F. PRICE.

Witnesses:

GEO. H. DANFORTH, F. B. OCoNNoR.

